The prior art illustrates various light shifting polymer compositions for use in the field of agriculture.
For example, Japanese Patent Application Nos. 06199814 and 05170969 disclose a light absorbing polymer composition containing an active additive from the group of pyrazine compounds. These patents teach that when the active additives are casted onto glass plates, the energy of the UV-light is transformed or shifted and then reflected in the blue spectral range. However, the use of such polymer compositions in agriculture is limited because blue light is not very effective in accelerating the growth and productivity of agriculture crops compared with light in the red spectral range. Russian author's certificate No. 2047624 to Minich et al. disclose a polymer composition which can be used in agriculture, containing an active additive in the form of a solid product. This product was obtained from the chemical reaction between europium nitrate, lanthanum nitrate and 1,10-phenanthroline as a solution in isopropanol.
This europium-lanthanum composition has some disadvantages; for example, the europium-lanthanum composition must be synthesized beforehand, then purified and dried. The size of the particles obtained during the synthesis are of rather large dimensions ranging size from a few microns or to tens or even hundreds of microns, which leads to an increase in light scattering by the film and consequently to the loss of light intensity because of the diffusion caused by the particles.